From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from outgoing.mit.edu (outgoing-auth-1.mit.edu [18.9.28.11]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 355703EAC8F for ; Thu, 25 Jun 2026 17:25:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=18.9.28.11 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782408347; cv=none; b=aOsbjeCKhaA/4bAtDJwhut0sQvVKMmE9+AmcMroSCS7775yKMXmbtyG/2ptC0Co/47wYIfsWZETMwpf2zQ4jHjm6BkXtzaG96RmJS3QWXO8MuNFddf2JeyTALMoUuA/sejTUheWkKB4KDqIwpSvzQ/TXJSk2j5Uv11gfDom2wzM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782408347; c=relaxed/simple; bh=8O0z6NM21IytQL/RKeSrTG52KWtD0u15OsIU6uvkf68=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=SMNJcSOYj0pH+0JTe57TfNKY11KUgXWFdhStSHpkh41xSgLuPwFXFtIEYgvVE5AWWLcX/7jC7Ydg5vFBQscU02Rk66c1whHHm8C25Bvy7tqVmRraDSuPbcSESgL14H2ssglwfzNFTWoN6z69VTbEdgObwuwMnhUVXjaGSL4eHck= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=mit.edu; spf=pass smtp.mailfrom=mit.edu; dkim=pass (2048-bit key) header.d=mit.edu header.i=@mit.edu header.b=UDDNOxPh; arc=none smtp.client-ip=18.9.28.11 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=mit.edu Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=mit.edu Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=mit.edu header.i=@mit.edu header.b="UDDNOxPh" Received: from trampoline.thunk.org (pool-108-26-156-113.bstnma.fios.verizon.net [108.26.156.113]) (authenticated bits=0) (User authenticated as tytso@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id 65PHMTFF003904 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 25 Jun 2026 13:22:30 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mit.edu; s=outgoing; t=1782408152; bh=10Hut2mNUeuBmzPVHLp1hncCuphKpgToxyugpIRx+4k=; h=From:Subject:Date:Message-ID:MIME-Version; b=UDDNOxPh6iiYw614Vh6rU2CQK+A/Fuufo1C0uoqsy787YR9i3bzS77uC00FeHlclT n6Gz8tJQ/3lrr3K0PvTOrnrvEUKPIftLTlVezRb+u2V/VT1zu9/jO/E2bLlAXl6m/J mOTdQD+aVquZlx73wrURFoFqOeTo49MssTYqmSIzoIlk3yXcwQG10R2KvMeulxlECS ka6OMa2c+WGZfKbAXypnoUPWrD+Kcv0B2IjdO9CItnCpZp3zpI4axi/xS0JGc1MHH/ aVFlG2Ry8sCEgfwECeju7Zz2ucAhKnLytmJqceFL5TQ/TmPKaOChzyv5EskkVgsU/G 8RAO7GXSTaV8g== Received: by trampoline.thunk.org (Postfix, from userid 15806) id F3CD12E3652; Thu, 25 Jun 2026 13:22:28 -0400 (EDT) From: "Theodore Ts'o" To: Ext4 Developers List , Matthew Wilcox Cc: "Theodore Ts'o" Subject: [PATCH RFC] ext4: enable scoped NOFS when starting a handle in nojournal mode Date: Thu, 25 Jun 2026 13:22:23 -0400 Message-ID: <20260625172223.88878-1-tytso@mit.edu> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The jbd2 layer enables NOFS mode using memalloc_nofs_{save,restore}() while a handle is active. We need to do the same in nojournal mode so that it is safe to remove GFP_NOFS flags while a jbd2 handle is active. This will require that we actually allocate a real handle, but with an h_invalid flag set, so there is a place to put the saved memalloc context. Signed-off-by: Theodore Ts'o --- fs/ext4/ext4_jbd2.c | 35 ++++++++++++++++++++++------------- fs/ext4/ext4_jbd2.h | 6 +----- include/linux/jbd2.h | 1 + 3 files changed, 24 insertions(+), 18 deletions(-) diff --git a/fs/ext4/ext4_jbd2.c b/fs/ext4/ext4_jbd2.c index 9a8c225f2753..c2f09cf4b506 100644 --- a/fs/ext4/ext4_jbd2.c +++ b/fs/ext4/ext4_jbd2.c @@ -35,12 +35,21 @@ static handle_t *ext4_get_nojournal(void) handle_t *handle = current->journal_info; unsigned long ref_cnt = (unsigned long)handle; - BUG_ON(ref_cnt >= EXT4_NOJOURNAL_MAX_REF_COUNT); - - ref_cnt++; - handle = (handle_t *)ref_cnt; - - current->journal_info = handle; + BUG_ON(handle && !handle->h_invalid); + + if (!handle) { + handle = jbd2_alloc_handle(GFP_NOFS); + if (!handle) + return ERR_PTR(-ENOMEM); + handle->h_invalid = 1; + /* + * This is done by start_this_handle() if journalling + * is enabled. + */ + handle->saved_alloc_context = memalloc_nofs_save(); + current->journal_info = handle; + } + handle->h_ref++; return handle; } @@ -48,14 +57,14 @@ static handle_t *ext4_get_nojournal(void) /* Decrement the non-pointer handle value */ static void ext4_put_nojournal(handle_t *handle) { - unsigned long ref_cnt = (unsigned long)handle; + BUG_ON(handle->h_ref == 0); - BUG_ON(ref_cnt == 0); - - ref_cnt--; - handle = (handle_t *)ref_cnt; - - current->journal_info = handle; + handle->h_ref--; + if (handle->h_ref == 0) { + memalloc_nofs_restore(handle->saved_alloc_context); + jbd2_free_handle(handle); + current->journal_info = NULL; + } } /* diff --git a/fs/ext4/ext4_jbd2.h b/fs/ext4/ext4_jbd2.h index 63d17c5201b5..75d4670d389c 100644 --- a/fs/ext4/ext4_jbd2.h +++ b/fs/ext4/ext4_jbd2.h @@ -182,15 +182,11 @@ handle_t *__ext4_journal_start_sb(struct inode *inode, struct super_block *sb, int rsv_blocks, int revoke_creds); int __ext4_journal_stop(const char *where, unsigned int line, handle_t *handle); -#define EXT4_NOJOURNAL_MAX_REF_COUNT ((unsigned long) 4096) - /* Note: Do not use this for NULL handles. This is only to determine if * a properly allocated handle is using a journal or not. */ static inline int ext4_handle_valid(handle_t *handle) { - if ((unsigned long)handle < EXT4_NOJOURNAL_MAX_REF_COUNT) - return 0; - return 1; + return !handle->h_invalid; } static inline void ext4_handle_sync(handle_t *handle) diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h index b68561187e90..7348fdadc810 100644 --- a/include/linux/jbd2.h +++ b/include/linux/jbd2.h @@ -513,6 +513,7 @@ struct jbd2_journal_handle unsigned int h_sync: 1; unsigned int h_reserved: 1; unsigned int h_aborted: 1; + unsigned int h_invalid: 1; unsigned int h_type: 8; unsigned int h_line_no: 16; -- 2.53.0